Abstract

The coal mining generates millions of tonnes of tailings containing pyrite (FeS2). The oxidation of pyrite in the presence of air and water, gives rise to an important environmental problem common in areas of coal mining, the generation of acid mine drainage (AMD). The oxidation of pyrite in the presence of water promotes the formation of H2SO4 (sulfuric acid) which promotes the release of iron in the form of Fe +2 and Fe +3, sulphates and a host of other metals such as Al, Mn and Zn. This prob ...

The coal mining generates millions of tonnes of tailings containing pyrite (FeS2). The oxidation of pyrite in the presence of air and water, gives rise to an important environmental problem common in areas of coal mining, the generation of acid mine drainage (AMD). The oxidation of pyrite in the presence of water promotes the formation of H2SO4 (sulfuric acid) which promotes the release of iron in the form of Fe +2 and Fe +3, sulphates and a host of other metals such as Al, Mn and Zn. This problem occurs quite intense in the coal in southern Brazil in particular in the states of Santa Catarina and Parana. The DAM produced by coal waste mining need to go through a treatment process in order to decrease the acidity and metal load discharged into the environment, in order to meet environmental requirements. The objective of this work was to study the production of a coagulant, ferric sulfate, with the following materials: (a) ferric sludge obtained by selective precipitation of DAM (b) obtained by reject coal concentration of the Layer Barro Branco, Santa Catarina, and (c) pyrite concentrate obtained by concentration of the tailings coal mine of Cambuí, Paraná. The methodology for the production of coagulant from sludge was the first in the selective precipitation of iron in pH 3.8, washing the precipitate with sulfuric acid and evaporation to obtain a solution with Fe 3 + concentration of approximately 12% with Fe2O3. The methodology for obtaining the coagulant from the pyrite present in coal or reject the pyrite concentrate was the percolation of water under oxidizing conditions to produce a liquor rich in ferric sulphate. Leach was also evaporated to obtain a solution of ferric sulphate with concentrations of Fe3 + up to approximately 12%. The quality of the coagulant was evaluated in terms of concentration of Fe, Al, Ca, Mn, Zn, Cu and sulfates. The results show that all the materials studied showed potential for production of the coagulant. Among the contaminants found, highlight the elements aluminum, calcium, manganese and zinc. However, the higher the sulfur content of the sample, the higher the yield and higher purity of the product. It was concluded that the processing of the waste coal to the concentration of pyrite to obtain ferric sulphate better. Coagulants produced were used in the treatment of sewage Campus do Vale UFRGS and water supply in the region of Porto Alegre. Ideas for use of tailings from coal mining are in line with the principles of the present time regarding the development and evaluation programs for waste and cleaner production. ...